external file defining responseContent outside of the soapUI project

Does anybody know how to use a file-system file as the responseContext to a web service call in the soapUI project file,
i.e. instead of

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" ...<br /><br />something like<br /><con:responseContent>file:\C:\...</con:responseContent><br /><br />( but this syntax does'nt seem to work&nbsp; <img src='http://community.smartbear.com/legacyfs/online/smilies/huh.gif'>)<br /><br />Any tips will be much appreciated!